1. Field of the Invention
The present invention relates to an intermediate transfer recording medium comprising a substrate film and a transfer portion, which is provided separably on the substrate film and comprises at least a receptive layer, a print formed by providing the intermediate transfer recording medium, thermally transferring an image onto the transfer portion, and then retransferring the transfer portion onto an object, and a method for image formation using the intermediate transfer recording medium.
2. Prior Art
Thermal transfer has become extensively used as a simple printing method. The thermal transfer is a method which comprises the steps of: putting a thermal transfer sheet, comprising a colorant layer provided on one side of a substrate sheet, on top of a thermal transfer image-receiving sheet optionally provided with an image-receptive layer; and image-wise heating the backside of the thermal transfer sheet by heating means such as a thermal head to selectively transfer the colorant contained in the colorant layer to form an image on the thermal transfer image-receiving sheet.
Thermal transfer methods are classified into thermal ink transfer (hot melt-type thermal transfer) and thermal dye sublimation transfer (sublimation-type thermal transfer). The thermal ink transfer is a method for image formation wherein a thermal transfer sheet comprising a substrate sheet, such as a PET film, bearing thereon a hot-melt ink layer, formed of a dispersion of a colorant, such as a pigment, in a binder, such as a hot-melt wax or resin, is provided and energy according to image information is applied to heating means such as a thermal head to transfer the colorant together with the binder onto a thermal transfer image-receiving sheet such as paper or plastic sheets. Images produced by the thermal ink transfer have high density and possess high sharpness and are suitable for recording binary images of characters or the like.
On the other hand, the thermal dye sublimation transfer is a method for image formation which comprises the steps of: providing a thermal transfer sheet comprising a substrate sheet, such as a PET film, bearing thereon a dye layer formed of a dye, which is mainly thermally transferred by sublimation, dissolved or dispersed in a resin binder; and applying energy according to image information to heating means such as a thermal head to transfer only the dye onto a thermal transfer image-receiving sheet comprising a substrate sheet, such as paper or a plastic, optionally provided with a dye-receptive layer. The thermal dye sublimation transfer can regulate the amount of the dye transferred according to the quantity of energy applied and thus can form gradation images of which the image density has been regulated dot by dot of the thermal head. Further, since the colorant used is a dye, the formed image is transparent, and the reproduction of intermediate colors produced by superimposing different color dyes on top of each other or one another is excellent. Accordingly, high-quality photograph-like full color images can be formed with excellent reproduction of intermediate colors by transferring different color dyes, such as yellow, magenta, cyan, and black, onto a thermal transfer image-receiving sheet, so as to superimpose the color dyes on top of each other or one another, from a thermal transfer sheet of the different colors.
Thermal transfer image-receiving sheets on which images will be formed by these thermal transfer methods have various practical applications. Representative examples of applications include proof sheets, and recording sheets for output images, output plans or designs drawn by CAD/CAM or the like, or images output from a variety of medical analyzers or measuring instruments such as CT scanners and endoscopic cameras. They can also be used as the alternative of instant photographs, and as paper for producing identity certifications, ID cards, credit cards, and other cards on which facial photographs or the like are printed, or for producing synthetic or memorial photographs which are taken at amusement facilities such as recreation parks, game centers, museums, aquariums and the like. The diversification of applications has led to an increasing demand for the thermal transfer of an image on any desired object. A method has been proposed, as one method for meeting this demand, wherein a colorant such as a dye or a pigment is transferred, from a thermal transfer sheet comprising a dye layer or a hot-melt ink layer, onto a receptive layer in an intermediate transfer recording medium comprising the receptive layer separably provided on a substrate to form an image on the receptive layer and, thereafter, the intermediate transfer recording medium is heated to transfer the receptive layer, with the image formed thereon, onto an object (Japanese Patent Laid-Open No. 238791/1987 or the like).
Since the use of the intermediate transfer recording medium permits the receptive layer to be transferred onto an object, this method is preferably used, for example, for objects, onto which a colorant is less likely to be transferred making it impossible to form high-quality images directly on them, and objects which are likely to be fused to the colorant layer at the time of thermal transfer. Therefore, the intermediate transfer recording medium is preferably used in the preparation of passports or other identity certifications, credit cards/ID cards, or other prints.
When a receptive layer is transferred onto an object from the above intermediate transfer recording medium, the transfer of a simple shape in a full density blotted form having an outer shape of a quadrangle, a circle or the like poses no severe problem. On the other hand, for example, when a void portion is provided in the transfer portion or when the outer edge shape is complicate, there occurs a problem that the edge of the receptive layer transferred onto the object is not sharp, and a portion not to be transferred is transferred, or a portion to be transferred is not transferred, resulting in unstable transfer of the receptive layer.
In particular, when the receptive layer in its portion not to be transferred is, for example, the place for writing of address, name or the like, or the place for sealing of a person, who has written the address, name or the like, or an issuer, the transfer of the receptive layer onto that portion even to a small extent renders the contents of the writing or the seal unsharp and thus poses a severe problem that the contents of the writing or the seal is illegible. To overcome the problem of unstability of the transfer of the receptive layer, a method is considered effective wherein, after the receptive layer is once transferred in a simple form, such as a quadrangle or a circle, a specialty layer, which permits writing and sealing thereon, is additionally provided by printing or the like. In this case, however, the provision of the additional specialty layer is troublesome and labor intensive and thus disadvantageously results in very high production cost.
Accordingly, it is an object of the present invention to solve the above problems of the prior art and to provide an intermediate transfer recording medium which comprises a substrate film and, separably provided on the substrate film, a transfer portion comprising at least a receptive layer, and, after the thermal transfer of an image onto the transfer portion, can retransfer the transfer portion onto an object while forming a nontransferred portion on a part of the object with high accuracy in a stable manner and, in addition, does not increase a production cost for providing a final print, and to provide a method for image formation using the intermediate transfer recording medium.